1. Field of the Invention
The present invention relates to an apparatus which involves generation of an electric field or a magnetic filed, and more particularly relates to such an apparatus in which manufacture, measurement or examination is carried out in the electric field or the magnetic field so that all object to be manufactured, measured or examined can be protected from being contaminated with particles produced in the apparatus.
2. Description of the Related Art
As a representative apparatus which involves generation of an electric field or a magnetic field, there are a plasma etching apparatus, a chemical vapor deposition (CVD) apparatus, a plasma sputtering apparatus, a focused ion beam (FIB) apparatus, an electron beam (EB) exposure apparatus, an electron microscopic apparatus and so on.
For example, the plasma etching apparatus is used to process an object to manufacture electronic devices. When the electronic devices are semiconductor devices, the object may be a semiconductor wafer. Also, when the electronic devices are liquid crystal display (LCD) panels, the object may be a glass substrate.
The plasma etching apparatus includes a housing having a bottom wall section, a side wall section and a top wall section which define a processing chamber. The plasma etching apparatus also includes an object stage provided in the processing chamber, a lower electrode incorporated in the object stage, and an upper electrode provided in the processing chamber so as to oppose the lower electrode. Note that the lower and upper electrodes are usually coated with a suitable dielectric material so that dielectric layers are formed thereon.
In operation, the object to be processed is mounted on the object stage, and a suitable etching gas is introduced into the processing chamber while applying a radio frequency (RF) voltage between the lower and upper electrodes to generate a plasma in the processing chamber, whereby the object is subjected to a plasma etching process.
Generally, during the etching process, reaction products, which are derived from the etching gas and the materials of the object, are produced and deposited on various internal members such as the object stage, the lower and upper electrodes, the wall sections of the housing and so on, so that reaction product deposits are formed as dielectric deposits on the internal members.
When the dielectric deposits are peeled from the internal members, many particles are produced in the processing chamber so that the object may be contaminated with the particles, resulting in occurrence of defects in the manufactured electronic devices.
As disclosed in, for example, JP-2003-068708 A and JP-2005-101539 A, the peeling of the dielectric deposits may be caused due to the fact that the dielectric deposits exist in an electric field defined between the lower and upper electrodes.
In particular, as disclosed in JP-2003-068708 A and JP-2005-101539 A, when reaction product deposits or dielectric deposits formed on an internal member exist in the electric field, they are subjected to a force which is defined by the following equation:F=ρE−(½)E2∇∈+(½)∇[E2m(d∈/dm)]wherein F is a force exerted on the dielectric deposits per unit volume, ρ is a density of true electric charge of the dielectric deposits, E is an electric field generated between the lower and upper electrodes, m is a mass density of the dielectric deposits, and ∈ is a permittivity of the dielectric deposits.
In the aforesaid equation, the first term “ρE”, represents a Coulomb force per unit volume, but the Coulomb force per unit volume can be ignored because the true electric charge density essentially does not exist in the dielectric deposits.
Also, the second term “(½)E2∇∈” represents a Maxwell stress, and the third term “(½)∇[E2m(d∈/dm)]” represents a Helmholtz stress.
JP-2003-068708 A discloses that the production of the particles in the processing chamber can be suppressed by controlling the Maxwell stress and the Helmholtz stress.
On the other hand, JP-2005-101539 A is directed to a cleaning method for the processing chamber by utilizing the Maxwell stress. Namely, it is disclosed that the Maxwell stress can be utilized to effectively remove the dielectric deposits from the internal members.